package virtfs

import (
	"context"
	"errors"
	"os"
	"testing"
	"time"
)

// ══════════════════════════════════════════════════════════════════
// NodeOption tests
// ══════════════════════════════════════════════════════════════════

func TestNodeOptions(t *testing.T) {
	t.Run("Stream", func(t *testing.T) {
		spec := FileNode("test", 0444, StreamRaw(func(ctx context.Context, base string) ([]byte, string, error) {
			return nil, "", nil
		}))
		if spec.Stream == nil {
			t.Error("Stream not set")
		}
	})

	t.Run("BlockOnce", func(t *testing.T) {
		spec := FileNode("test", 0444, BlockOnceRaw(func(ctx context.Context, base string) ([]byte, string, error) {
			return nil, "", nil
		}))
		if spec.BlockOnce == nil {
			t.Error("BlockOnce not set")
		}
	})

	t.Run("Request", func(t *testing.T) {
		spec := FileNode("test", 0666, Request(func(_ context.Context, data []byte) ([]byte, error) {
			return nil, nil
		}))
		if spec.Request == nil {
			t.Error("Request not set")
		}
	})

	t.Run("RemoveNode", func(t *testing.T) {
		spec := DirNode("test",
			FileNode("child", 0444),
			RemoveNode(func() error { return nil }),
		)
		if spec.Remove == nil {
			t.Error("Remove not set")
		}
	})

	t.Run("StatOverride", func(t *testing.T) {
		spec := FileNode("test", 0444, StatOverride(func() os.FileInfo {
			return &SyntheticFileInfo{Name_: "test"}
		}))
		if spec.Stat == nil {
			t.Error("Stat not set")
		}
	})

	t.Run("UID", func(t *testing.T) {
		spec := FileNode("test", 0444, UID("owner"))
		if spec.UID != "owner" {
			t.Errorf("UID = %q, want 'owner'", spec.UID)
		}
	})

	t.Run("GID", func(t *testing.T) {
		spec := FileNode("test", 0444, GID("group"))
		if spec.GID != "group" {
			t.Errorf("GID = %q, want 'group'", spec.GID)
		}
	})

	t.Run("Doc", func(t *testing.T) {
		spec := FileNode("test", 0444, Doc("description"))
		if spec.Desc != "description" {
			t.Errorf("Desc = %q", spec.Desc)
		}
	})
}

// ══════════════════════════════════════════════════════════════════
// Tree tests
// ══════════════════════════════════════════════════════════════════

func TestTreeMount(t *testing.T) {
	parent := &Tree{perm: 0755}
	child := &Tree{perm: 0755}
	child.listFn = func(_ []string) ([]os.DirEntry, error) {
		return []os.DirEntry{fileEntry("childfile", 0444)}, nil
	}

	parent.Mount("subdir", child)

	got := parent.Child("subdir")
	if got != child {
		t.Error("Child did not return mounted child")
	}

	children := parent.Children()
	if len(children) != 1 {
		t.Errorf("Children = %d, want 1", len(children))
	}

	nilChild := parent.Child("nonexistent")
	if nilChild != nil {
		t.Error("Child should return nil for nonexistent")
	}
}

func TestTreeSplit(t *testing.T) {
	parent := &Tree{perm: 0755}
	child := &Tree{perm: 0755}
	parent.Mount("sub", child)

	c, rest, ok := parent.split("sub")
	if !ok || c != child || rest != "" {
		t.Error("split exact match failed")
	}

	c2, rest2, ok2 := parent.split("sub/file")
	if !ok2 || c2 != child || rest2 != "file" {
		t.Error("split prefix match failed")
	}

	_, _, ok3 := parent.split("other")
	if ok3 {
		t.Error("split should not find 'other'")
	}
}

// ══════════════════════════════════════════════════════════════════
// fileConfig tests
// ══════════════════════════════════════════════════════════════════

func TestFileConfigMethods(t *testing.T) {
	fc := &fileConfig{
		StatFn:         func() (os.FileInfo, error) { return &SyntheticFileInfo{Name_: "test"}, nil },
		ReadFn:         func() ([]byte, error) { return []byte("content"), nil },
		WriteFn:        func(data []byte) error { return nil },
		BlockingReadFn: func(ctx context.Context, base string) ([]byte, string, error) { return nil, "", nil },
	}

	fi, err := fc.Stat()
	if err != nil || fi.Name() != "test" {
		t.Error("Stat failed")
	}
	data, err := fc.Read()
	if err != nil || string(data) != "content" {
		t.Error("Read failed")
	}
	if err := fc.Write([]byte("x")); err != nil {
		t.Error("Write failed")
	}
	if _, _, err := fc.BlockingRead(context.Background(), ""); err != nil {
		t.Error("BlockingRead failed")
	}
}

func TestFileConfigModes(t *testing.T) {
	fc := &fileConfig{}
	if fc.BlockingReadMode() || fc.StreamMode() || fc.RequestRespMode() {
		t.Error("default modes should be false")
	}

	if !(&fileConfig{BlockingRead_: true}).BlockingReadMode() {
		t.Error("BlockingReadMode should be true")
	}
	if !(&fileConfig{StreamMode_: true}).StreamMode() {
		t.Error("StreamMode should be true")
	}
	if !(&fileConfig{RequestResp_: true}).RequestRespMode() {
		t.Error("RequestRespMode should be true")
	}
}

// ══════════════════════════════════════════════════════════════════
// Builder tests - delete/rename operations
// ══════════════════════════════════════════════════════════════════

func TestDeleteDir(t *testing.T) {
	var deleted bool
	spec := DirNode("/",
		Each("{id}", func() ([]FsNodeDecl, error) {
			return []FsNodeDecl{{
				Name:   "item",
				Remove: func() error { deleted = true; return nil },
				Children: []FsNodeDecl{
					FileNode("data", 0444),
				},
			}}, nil
		}),
	)

	tree := BuildTree(spec)
	err := tree.Delete("item")
	if err != nil {
		t.Fatalf("Delete: %v", err)
	}
	if !deleted {
		t.Error("remove handler not called")
	}
}

func TestDeleteDirNotFound(t *testing.T) {
	spec := DirNode("/", FileNode("file", 0444))
	tree := BuildTree(spec)
	if err := tree.Delete("nonexistent"); err == nil {
		t.Error("Delete should fail for nonexistent")
	}
}

func TestRenameDir(t *testing.T) {
	var newName string
	spec := DirNode("/",
		Each("{id}", func() ([]FsNodeDecl, error) {
			return []FsNodeDecl{{
				Name:   "item",
				Rename: func(n string) error { newName = n; return nil },
				Children: []FsNodeDecl{
					FileNode("data", 0444),
				},
			}}, nil
		}),
	)

	tree := BuildTree(spec)
	if err := tree.Rename("item", "newitem"); err != nil {
		t.Fatalf("Rename: %v", err)
	}
	if newName != "newitem" {
		t.Errorf("newName = %q, want 'newitem'", newName)
	}
}

func TestRenameDirNotFound(t *testing.T) {
	spec := DirNode("/", FileNode("file", 0444))
	tree := BuildTree(spec)
	if err := tree.Rename("nonexistent", "new"); err == nil {
		t.Error("Rename should fail for nonexistent")
	}
}

// ══════════════════════════════════════════════════════════════════
// Builder tests - blocking modes
// ══════════════════════════════════════════════════════════════════

func TestOpenLeafBlockOnce(t *testing.T) {
	spec := DirNode("/",
		FileNode("blocking", 0444, BlockOnceRaw(func(ctx context.Context, base string) ([]byte, string, error) {
			return []byte("data"), "next", nil
		})),
	)
	tree := BuildTree(spec)
	f, err := tree.Open("blocking")
	if err != nil {
		t.Fatalf("Open: %v", err)
	}
	if !f.BlockingReadMode() {
		t.Error("expected BlockingReadMode")
	}
}

func TestOpenLeafStream(t *testing.T) {
	spec := DirNode("/",
		FileNode("streaming", 0444, StreamRaw(func(ctx context.Context, base string) ([]byte, string, error) {
			return []byte("stream"), "cursor", nil
		})),
	)
	tree := BuildTree(spec)
	f, err := tree.Open("streaming")
	if err != nil {
		t.Fatalf("Open: %v", err)
	}
	if !f.StreamMode() {
		t.Error("expected StreamMode")
	}
}

func TestOpenLeafRequest(t *testing.T) {
	spec := DirNode("/",
		FileNode("request", 0666, Request(func(_ context.Context, data []byte) ([]byte, error) {
			return append([]byte("echo:"), data...), nil
		})),
	)
	tree := BuildTree(spec)
	f, err := tree.Open("request")
	if err != nil {
		t.Fatalf("Open: %v", err)
	}
	if !f.RequestRespMode() {
		t.Error("expected RequestRespMode")
	}
	if err := f.Write([]byte("test")); err != nil {
		t.Fatalf("Write: %v", err)
	}
	data, err := f.Read()
	if err != nil {
		t.Fatalf("Read: %v", err)
	}
	if string(data) != "echo:test" {
		t.Errorf("data = %q, want 'echo:test'", data)
	}
}

func TestOpenLeafRequestError(t *testing.T) {
	spec := DirNode("/",
		FileNode("request", 0666, Request(func(_ context.Context, data []byte) ([]byte, error) {
			return nil, errors.New("request error")
		})),
	)
	tree := BuildTree(spec)
	f, err := tree.Open("request")
	if err != nil {
		t.Fatalf("Open: %v", err)
	}
	if err := f.Write([]byte("test")); err == nil {
		t.Error("Write should fail when request returns error")
	}
}

func TestOpenLeafRequestWithFallbackRead(t *testing.T) {
	spec := DirNode("/",
		FileNode("request", 0666,
			Read(func() ([]byte, error) { return []byte("fallback"), nil }),
			Request(func(_ context.Context, data []byte) ([]byte, error) { return []byte("response"), nil }),
		),
	)
	tree := BuildTree(spec)
	f, err := tree.Open("request")
	if err != nil {
		t.Fatalf("Open: %v", err)
	}
	data, err := f.Read()
	if err != nil {
		t.Fatalf("Read: %v", err)
	}
	if string(data) != "fallback" {
		t.Errorf("data = %q, want 'fallback'", data)
	}
}

func TestOpenLeafRequestCancelOnClose(t *testing.T) {
	canceled := make(chan struct{})
	started := make(chan struct{})
	spec := DirNode("/",
		FileNode("request", 0666, Request(func(ctx context.Context, data []byte) ([]byte, error) {
			close(started)
			<-ctx.Done()
			close(canceled)
			return nil, ctx.Err()
		})),
	)
	tree := BuildTree(spec)
	f, err := tree.Open("request")
	if err != nil {
		t.Fatalf("Open: %v", err)
	}

	// Start the request in a goroutine
	done := make(chan error, 1)
	go func() {
		done <- f.Write([]byte("test"))
	}()

	// Wait for request to start
	<-started

	// Close should cancel the context
	f.Close()

	// Verify context was canceled
	select {
	case <-canceled:
		// Success
	case <-time.After(time.Second):
		t.Fatal("context was not canceled on close")
	}

	// Write should return with context canceled error
	select {
	case err := <-done:
		if err == nil || err != context.Canceled {
			t.Errorf("Write error = %v, want context.Canceled", err)
		}
	case <-time.After(time.Second):
		t.Fatal("Write did not return after close")
	}
}

func TestOpenLeafNoWriteHandler(t *testing.T) {
	spec := DirNode("/",
		FileNode("readonly", 0444, Read(func() ([]byte, error) { return []byte("data"), nil })),
	)
	tree := BuildTree(spec)
	f, err := tree.Open("readonly")
	if err != nil {
		t.Fatalf("Open: %v", err)
	}
	if err := f.Write([]byte("test")); err == nil {
		t.Error("Write should fail on read-only file")
	}
}

func TestOpenLeafNoReadHandler(t *testing.T) {
	spec := DirNode("/",
		FileNode("noread", 0222, Write(func(data []byte) error { return nil })),
	)
	tree := BuildTree(spec)
	f, err := tree.Open("noread")
	if err != nil {
		t.Fatalf("Open: %v", err)
	}
	data, err := f.Read()
	if err != nil {
		t.Fatalf("Read: %v", err)
	}
	if len(data) != 0 {
		t.Errorf("data = %q, want empty", data)
	}
}

func TestOpenLeafStatWithCustomStat(t *testing.T) {
	spec := DirNode("/",
		FileNode("custom", 0444, StatOverride(func() os.FileInfo {
			return &SyntheticFileInfo{Name_: "customname", Size_: 999, Mode_: 0777}
		})),
	)
	tree := BuildTree(spec)
	f, err := tree.Open("custom")
	if err != nil {
		t.Fatalf("Open: %v", err)
	}
	fi, err := f.Stat()
	if err != nil {
		t.Fatalf("Stat: %v", err)
	}
	if fi.Name() != "customname" || fi.Size() != 999 {
		t.Errorf("got Name=%q Size=%d", fi.Name(), fi.Size())
	}
}

func TestOpenLeafDefaultBlockingRead(t *testing.T) {
	spec := DirNode("/",
		FileNode("normal", 0444, Read(func() ([]byte, error) { return []byte("data"), nil })),
	)
	tree := BuildTree(spec)
	f, err := tree.Open("normal")
	if err != nil {
		t.Fatalf("Open: %v", err)
	}
	if _, _, err := f.BlockingRead(context.Background(), ""); err == nil {
		t.Error("BlockingRead should fail for non-blocking file")
	}
}

// ══════════════════════════════════════════════════════════════════
// Builder tests - validation
// ══════════════════════════════════════════════════════════════════

func TestValidateDirWithFileHandlers(t *testing.T) {
	defer func() {
		if r := recover(); r == nil {
			t.Error("should panic for dir with file handlers")
		}
	}()

	spec := DirNode("/",
		FileNode("child", 0444),
		Read(func() ([]byte, error) { return nil, nil }),
	)
	BuildTree(spec)
}

func TestValidateMultipleBlockingModes(t *testing.T) {
	defer func() {
		if r := recover(); r == nil {
			t.Error("should panic for multiple blocking modes")
		}
	}()

	spec := DirNode("/",
		FileNode("bad", 0444,
			BlockOnceRaw(func(context.Context, string) ([]byte, string, error) { return nil, "", nil }),
			StreamRaw(func(context.Context, string) ([]byte, string, error) { return nil, "", nil }),
		),
	)
	BuildTree(spec)
}

func TestValidateTemplateWithoutBindings(t *testing.T) {
	defer func() {
		if r := recover(); r == nil {
			t.Error("should panic for template without bindings")
		}
	}()

	spec := DirNode("/", FileNode("{id}", 0444))
	BuildTree(spec)
}

// ══════════════════════════════════════════════════════════════════
// Builder tests - Each with closure capture
// ══════════════════════════════════════════════════════════════════

func TestEachClosureCapture(t *testing.T) {
	type Item struct{ Name, Value string }
	items := []Item{{"foo", "hello"}, {"bar", "world"}}

	spec := DirNode("/",
		Each("{item}", func() ([]FsNodeDecl, error) {
			var out []FsNodeDecl
			for _, item := range items {
				it := item
				out = append(out, FsNodeDecl{
					Name: it.Name,
					Children: []FsNodeDecl{
						FileNode("value", 0444, Read(func() ([]byte, error) {
							return []byte(it.Value), nil
						})),
					},
				})
			}
			return out, nil
		}),
	)

	tree := BuildTree(spec)

	// Read foo/value
	f, err := tree.Open("foo/value")
	if err != nil {
		t.Fatalf("Open foo/value: %v", err)
	}
	data, err := f.Read()
	if err != nil {
		t.Fatalf("Read: %v", err)
	}
	if string(data) != "hello" {
		t.Errorf("foo/value = %q, want 'hello'", data)
	}

	// Read bar/value
	f2, err := tree.Open("bar/value")
	if err != nil {
		t.Fatalf("Open bar/value: %v", err)
	}
	data2, err := f2.Read()
	if err != nil {
		t.Fatalf("Read: %v", err)
	}
	if string(data2) != "world" {
		t.Errorf("bar/value = %q, want 'world'", data2)
	}
}

func TestEachDirListing(t *testing.T) {
	spec := DirNode("/",
		Each("{item}", func() ([]FsNodeDecl, error) {
			return []FsNodeDecl{
				{Name: "alpha", Children: []FsNodeDecl{FileNode("x", 0444)}},
				{Name: "beta", Children: []FsNodeDecl{FileNode("x", 0444)}},
			}, nil
		}),
	)

	tree := BuildTree(spec)
	entries, err := tree.List()
	if err != nil {
		t.Fatalf("List: %v", err)
	}
	if len(entries) != 2 {
		t.Fatalf("got %d entries, want 2", len(entries))
	}
	if entries[0].Name() != "alpha" || entries[1].Name() != "beta" {
		t.Errorf("entries = %v, %v", entries[0].Name(), entries[1].Name())
	}
}

func TestEachWithAliases(t *testing.T) {
	spec := DirNode("/",
		Each("{item}", func() ([]FsNodeDecl, error) {
			return []FsNodeDecl{{
				Name:    "friendly",
				Aliases: []string{"uuid-123"},
				Children: []FsNodeDecl{
					FileNode("name", 0444, Read(func() ([]byte, error) { return []byte("found"), nil })),
				},
			}}, nil
		}),
	)

	tree := BuildTree(spec)
	// Access by alias
	f, err := tree.Open("uuid-123/name")
	if err != nil {
		t.Fatalf("Open by alias: %v", err)
	}
	data, err := f.Read()
	if err != nil {
		t.Fatalf("Read: %v", err)
	}
	if string(data) != "found" {
		t.Errorf("data = %q", data)
	}
}

func TestStatDir(t *testing.T) {
	spec := DirNode("/",
		Each("{item}", func() ([]FsNodeDecl, error) {
			return []FsNodeDecl{{
				Name:     "sub",
				Children: []FsNodeDecl{FileNode("file", 0444)},
			}}, nil
		}),
	)

	tree := BuildTree(spec)
	fi, err := tree.Stat("sub")
	if err != nil {
		t.Fatalf("Stat: %v", err)
	}
	if !fi.IsDir() {
		t.Error("sub should be a directory")
	}
}

func TestStatFile(t *testing.T) {
	spec := DirNode("/",
		FileNode("readme", 0644, Read(func() ([]byte, error) { return []byte("hi"), nil })),
	)

	tree := BuildTree(spec)
	fi, err := tree.Stat("readme")
	if err != nil {
		t.Fatalf("Stat: %v", err)
	}
	if fi.IsDir() {
		t.Error("readme should not be a directory")
	}
	if fi.Mode() != 0644 {
		t.Errorf("mode = %o, want 0644", fi.Mode())
	}
}

func TestNestedPath(t *testing.T) {
	spec := DirNode("/",
		DirNode("a",
			DirNode("b",
				FileNode("c", 0444, Read(func() ([]byte, error) { return []byte("deep"), nil })),
			),
		),
	)

	tree := BuildTree(spec)
	f, err := tree.Open("a/b/c")
	if err != nil {
		t.Fatalf("Open a/b/c: %v", err)
	}
	data, err := f.Read()
	if err != nil {
		t.Fatalf("Read: %v", err)
	}
	if string(data) != "deep" {
		t.Errorf("data = %q, want 'deep'", data)
	}
}

// ══════════════════════════════════════════════════════════════════
// GenerateHelp test
// ══════════════════════════════════════════════════════════════════

func TestGenerateHelp(t *testing.T) {
	spec := DirNode("/",
		FileNode("ctl", 0222, Doc("Control file")),
		FileNode("info", 0444, Doc("Server info")),
	)
	help := GenerateHelp(spec)
	if help == "" {
		t.Error("help is empty")
	}
	if !contains(help, "ctl") || !contains(help, "Control file") {
		t.Errorf("help missing ctl: %q", help)
	}
}

func contains(s, sub string) bool {
	return len(s) >= len(sub) && (s == sub || len(s) > 0 && containsStr(s, sub))
}

func containsStr(s, sub string) bool {
	for i := 0; i <= len(s)-len(sub); i++ {
		if s[i:i+len(sub)] == sub {
			return true
		}
	}
	return false
}